Process for strengthening porous 3D printed objects

ABSTRACT

A composite body includes a bound mixture, a resin and a coating. The bound mixture includes a binder and a plurality of particles. The resin fully infiltrates the bound mixture such that the resin fully infiltrates an entire thickness of the bound mixture. The composite body is formed by combining a plurality of particles with a binder to form a bound mixture and infiltrating the bound mixture with a resin to a depth such that substantially an entire thickness of the bound mixture contains the resin. The coating defines an outer layer of the composite body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/707,598, filed on Sep. 18, 2017, which claims the benefit of thefiling date of U.S. Provisional Patent Application No. 62/398,271 filedSep. 22, 2016, the disclosure of which is hereby incorporated herein byreference.

FIELD OF THE TECHNOLOGY

The present technology relates generally to the preparation of articlesformed of bound particulates, and in particular to the strengthening ofsuch articles, especially with respect to such articles formed bythree-dimensional (“3D”) printing.

BACKGROUND OF THE TECHNOLOGY

Additive manufacturing technologies, such as 3D printing, have beenemployed to rapidly produce casting molds as well as end products withcomplex geometries, e.g., articles requiring undercuts. Binder jetting,a generally lower cost 3D printing process, involves extruding a liquid,or otherwise sufficiently flowable, polymer binder from a nozzle, onto abed of a particle composition in a controlled manner using a traditionalmultiple array inkjet print head to form and fuse patterned layers intoan article substantially corresponding to a prepared 3D computer model.Machines for 3D binder jet printing of particle compositions aremanufactured by companies such as Voxeljet AG, The ExOne Company, LLC,and Zcorp, Inc.

Due to the relative low cost compared to other materials, silica sandhas been used as a bound particulate in 3D printing by a growing numberof industries to produce molds for final castings, especially for use incasting large metallic components which are prepared by pouring moltenmetal into a mold cavity formed by a sand casting. However, articlesprepared by 3D sand printing have exhibited poor structuralcharacteristics, such as lower flexural strengths, and thus the use ofsand has been inadequate for preparing functional parts. Also, theproduction of large thin-walled sand parts has not been possible due totheir high likelihood of breakage during handling.

Thus, improvements are needed to form either or both of stronger andlarger thin-walled, low-cost 3D printed articles.

SUMMARY OF THE TECHNOLOGY

In accordance with an aspect of the technology, a plurality ofparticles, such as but not limited to sand or powdered materialsdescribed further herein, may be bound into a base body in the shape ofa predetermined article. Such article may correspond or substantiallycorrespond to a prepared 3D computer model. Either or both of theoutside and inside surfaces of the base body may be infiltrated (i.e.,impregnated) with a curable resin to form a composite body of increasedstrength, in particular increased flexural strength, relative to thebase body alone. The depth of diffusion of the curable resin into thebase body may vary based on a number of factors, in particular theamount of resin that is applied to the base body. The base body may bedesigned and may be subsequently formed such that excess particles maybe removed from the base body after application of the resin. Additionalcoatings or back-fillings, such as but not limited to spraymetallization, fiber strands, a fiber weave, metal plating, or drypowders may be added to the base body to give additional strength or adesired finish to the composite body.

In this manner, the printed part is imparted with a higher strength thanpreviously sand-printed articles.

In accordance with another aspect of the technology, a composite bodymay include a bound mixture and a resin. The bound mixture may include abinder and a plurality of particles. The resin may fully infiltrate thebound mixture such that the resin fully infiltrates an entire thicknessof the composite body.

In some arrangements, the bound mixture consists of the binder and theplurality of particles meaning the bound mixture only includes thebinder and the plurality of particles.

In some arrangements, the bound mixture may define pores into which theresin is infiltrated.

In some arrangements, the composite body may further include a coatingapplied to the bound mixture. In some such arrangements, the coating mayform an outer layer of the composite body. In some arrangements, thecoating may be any one or any combination of a spray metallization,fiber strands, a fiber weave, metal plating, or dry powders. Coatingsmay be wholly or partially made of zinc, aluminum, copper, steel,nickel, titanium, silver, gold, tantalum, cobalt chromium, or alloys ofthese metals as well as cermets including tungsten carbide cobalt andceramics including alumina and chromium carbide.

In some arrangements, such fiber strands and such fiber weave may be anyone or any combination of fiberglass, carbon fiber, and an aramid fiber.In some arrangements, such fiber strands and such fiber weave may beembedded in the resin. In some arrangements, fiber strands may be anyone or any combination of chopped, loose, and mat. Such spraymetallization may be any one or any combination of an arc spraying,thermal or flame spraying, and kinetic or cold spraying.

In some arrangements, the coating may be metallic plating, such as butnot limited to any one or any combination of copper, nickel, and chromeplating. Metallic plating may be performed using electroplating orelectroless plating. In some examples of electroplating, electricallyconductive dry powders may be added to the resin before the resin fullycures or a conductive coating may be applied onto the composite body. Anelectrically charged plating material, e.g., electrolytic copper, maythen be applied to the conductive powders or other conductive coatingthat has been applied to the composite body.

In some arrangements, the dry powders may be metallic or ceramicparticles.

In some arrangements, the binder may be one part of a two-part curableresin.

In some arrangements, the plurality of particles may be made of any oneor any combination of a sand, sodium bicarbonate, polymer, plaster,metal, ceramic, ash, organic powders, e.g., corn cob powder, includingedible powders, and other particles which preferably may have a largesurface area or may be porous and preferably may be more flexible, e.g.,relative to sand, including but not limited to engineered particles. Insome arrangements, the plurality of particles may be solid. In somearrangements, the plurality of particles may be hollow.

In some arrangements, the composite body may be in the form of an atleast partially hollow shell.

In some arrangements, the resin may have been applied from a pluralityof directions to define a part line.

In some arrangements, the bound mixture may define a gradient porositywithin the composite body.

In some arrangements, the porosity of an interior of the composite bodymay be greater than the porosity of an exterior of the composite bodyopposite the interior of the composite body.

In some arrangements, the composite body may be a first composite bodyfused to a second composite body, which may be in the same form as thefirst composite body, to define a combined construct. In somearrangements, the composite body may define a core, and a shell may atleast partially surround the core to define a combined construct. Insome such arrangements, the shell may be a carbon fiber shell.

In accordance with another aspect of the technology, a composite bodymay be formed by a process. In this process, a plurality of particlesmay be combined with a binder to form a bound mixture. The bound mixturemay be infiltrated with a resin to a depth such that substantially anentire thickness of the composite body contains the resin. In somearrangements, all of the bound mixture of the composite body may beinfiltrated with the resin.

In some arrangements, in combining the plurality of particles with thebinder, the binder may be printed through a 3D printing head ontoparticles supported by a substrate. In some arrangements, unboundparticles supported by the substrate may be separated from the compositebody. In some arrangements, particles supported by the substrate may notadhere to each other.

In some arrangements, a portion or portions of the bound mixture may beremoved such that substantially the entire thickness of the compositebody contains the resin.

In some arrangements, in combining the plurality of particles with thebinder, a bound mixture may be formed around unbound particles. In somearrangements, in combining the plurality of particles with the binder, afirst section defined by unit cells may be formed extending from asecond section. In some such arrangements, the second section may besubstantially solid.

In some arrangements, the bound mixture infiltrated with the resin maybe coated. In some such arrangements, the coating may form an outerlayer of the composite body. In some arrangements, the coating may beany one or any combination of a spray metallization, fiber strands, afiber weave, metal plating, or dry powders. Coatings may be wholly orpartially made of zinc, aluminum, copper, steel, nickel, titanium,silver, gold, tantalum, cobalt chromium, or alloys of these metals aswell as cermets including tungsten carbide cobalt and ceramics includingalumina and chromium carbide.

In some arrangements, such fiber strands and such fiber weave may be anyone or any combination of fiberglass, carbon fiber, and an aramid fiber.In some arrangements, such fiber strands and such fiber weave may beembedded in the resin. In some arrangements, fiber strands may be anyone or any combination of chopped, loose, and mat. Such spraymetallization may be any one or any combination of an arc spraying,thermal or flame spraying, and kinetic or cold spraying.

In some arrangements, the coating may be metallic plating, such as butnot limited to any one or any combination of copper, nickel, and chromeplating. Metallic plating may be performed using electroplating orelectroless plating. In some examples of electroplating, electricallyconductive dry powders may be added to the resin before the resin fullycures or a conductive coating may be applied onto the composite body. Anelectrically charged plating material, e.g., electrolytic copper, maythen be applied to the conductive powders or other conductive coatingthat has been applied to the composite body.

In some arrangements, the dry powders may be metallic or ceramicparticles.

In some arrangements, the coating may surround the bound mixtureinfiltrated with the resin. In some such arrangements, unbound particlesinside the coating may be removed.

In accordance with another aspect of the technology, a composite bodymay include a bound mixture that may include a binder and a firstplurality of particles, a second plurality of particles, and a resin.The bound mixture may define a surface area. The second plurality ofparticles may be unbound by the binder. The resin may infiltrate theentire surface area of the bound mixture such that the resin-infiltratedsurface area of the bound mixture may surround and may retain the secondplurality of particles.

In some arrangements, the bound mixture consists of the binder and thefirst plurality of particles meaning the bound mixture only includes thebinder and the first plurality of particles.

In accordance with another aspect of the technology, a composite bodymay include a bound mixture that may include a binder and a firstplurality of particles, a second plurality of particles, and a resin.The resin may infiltrate the bound mixture without infiltrating thesecond plurality of particles such that the resin-infiltrated boundmixture may surround and may retain the second plurality of particles.

In some arrangements, the bound mixture consists of the binder and thefirst plurality of particles meaning the bound mixture only includes thebinder and the first plurality of particles.

In some arrangements, the second plurality of particles may be made of adifferent material than the first plurality of particles. In otherarrangements, the second plurality of particles may be made of the samematerial as the first plurality of particles.

In some arrangements, the binder may be a first binder and the boundmixture may be a first bound mixture, and the second plurality ofparticles may be combined with a second binder to form a second boundmixture. In some such arrangements, the first and second binders may bemade of the same material. In some such arrangements, the secondplurality of particles may be made of the same material as the firstplurality of particles such that the first bound mixture is the same asthe second bound mixture. In some arrangements, the first and secondbinders may be made of a different material. In some arrangements, thesecond plurality of particles may be unbound particles.

In some arrangements, the bound mixture may define pores into which theresin is infiltrated.

In some arrangements, the composite body may further include a coatingapplied to the bound mixture. In some such arrangements, the coating mayform an outer layer of the composite body. In some arrangements, thecoating may be any one or any combination of a spray metallization,fiber strands, a fiber weave, metal plating, or dry powders. Coatingsmay be wholly or partially made of zinc, aluminum, copper, steel,nickel, titanium, silver, gold, tantalum, cobalt chromium, or alloys ofthese metals as well as cermets including tungsten carbide cobalt andceramics including alumina and chromium carbide.

In some arrangements, such fiber strands and such fiber weave may be anyone or any combination of fiberglass, carbon fiber, and an aramid fiber.In some arrangements, such fiber strands and such fiber weave may beembedded in the resin. In some arrangements, fiber strands may be anyone or any combination of chopped, loose, and mat. Such spraymetallization may be any one or any combination of an arc spraying,thermal or flame spraying, and kinetic or cold spraying.

In some arrangements, the coating may be metallic plating, such as butnot limited to any one or any combination of copper, nickel, and chromeplating. Metallic plating may be performed using electroplating orelectroless plating. In some examples of electroplating, electricallyconductive dry powders may be added to the resin before the resin fullycures or a conductive coating may be applied onto the composite body. Anelectrically charged plating material, e.g., electrolytic copper, maythen be applied to the conductive powders or other conductive coatingthat has been applied to the composite body.

In some arrangements, the dry powders may be metallic or ceramicparticles.

In some arrangements, the binder may be one part of a two-part curableresin.

In some arrangements, either or both of the first plurality of particlesand the second plurality of particles may be made of any one or anycombination of a sand, sodium bicarbonate, polymer, plaster, metal,ceramic, ash, organic powders, e.g., corn cob powder, including ediblepowders, and other particles which preferably may have a large surfacearea or may be porous and preferably may be more flexible, e.g.,relative to sand, including but not limited to engineered particles. Insome arrangements, either or both of the first plurality of particlesand the second plurality of particles may be solid. In somearrangements, either or both of the first plurality of particles and thesecond plurality of particles may be hollow.

In some arrangements, the composite body may be in the form of an atleast partially hollow shell.

In some arrangements, the resin may have been applied from a pluralityof directions to define a part line.

In some arrangements, the bound mixture may define a gradient porositywithin the composite body.

In some arrangements, the porosity of an interior of the composite bodymay be greater than the porosity of an exterior of the composite bodyopposite the interior of the composite body.

In some arrangements, the composite body may be a first composite bodyfused to a second composite body, which may be in the same form as thefirst composite body, to define a combined construct. In somearrangements, the composite body may define a core, and a shell may atleast partially surround the core to define a combined construct. Insome such arrangements, the shell may be a carbon fiber shell.

In accordance with another aspect of the technology, a composite bodymay be formed by a process. In this process, a first plurality ofparticles may be combined with a binder to form a bound mixture. Anentire surface area of the bound mixture may be infiltrated with a resinsuch that the resin-infiltrated surface area of the bound mixturesurrounds and retains a second plurality of particles unbound by thebinder. In some arrangements, all of the bound mixture of the compositebody may be infiltrated with the resin.

In some arrangements, the bound mixture consists of the binder and thefirst plurality of particles meaning the bound mixture only includes thebinder and the first plurality of particles.

In accordance with another aspect of the technology, a composite bodymay be formed by a process. In this process, a first plurality ofparticles may be combined with a binder to form a bound mixture. Thebound mixture may be infiltrated with a resin such that theresin-infiltrated bound mixture may surround and may retain the secondplurality of particles without infiltrating the second plurality ofparticles.

In some arrangements, the first bound mixture consists of the binder andthe first plurality of particles meaning the bound mixture only includesthe binder and the first plurality of particles.

In some arrangements, the second plurality of particles may be made of adifferent material than the first plurality of particles. In otherarrangements, the second plurality of particles may be made of the samematerial as the first plurality of particles.

In some arrangements, the binder may be a first binder and the boundmixture may be a first bound mixture, and the second plurality ofparticles may be combined with a second binder to form a second boundmixture. In some such arrangements, the first and second binders may bemade of the same material. In some such arrangements, the secondplurality of particles may be the same as the first plurality ofparticles such that the first bound mixture is the same as the secondbound mixture. In some arrangements, the first and second binders may bemade of a different material. In some arrangements, the second pluralityof particles may be unbound particles.

In some arrangements, in combining the first plurality of particles withthe binder, the binder may be printed through a 3D printing head ontoparticles supported by a substrate. In some arrangements, unboundparticles supported by the substrate may be separated from the compositebody. In some arrangements, particles supported by the substrate may notadhere to each other.

In some arrangements, a portion or portions of the bound mixture may beremoved such that substantially the entire thickness of the compositebody contains the resin.

In some arrangements, in combining the first plurality of particles withthe binder, a first section defined by unit cells may be formedextending from a second section. In some such arrangements, the secondsection may be substantially solid.

In some arrangements, the bound mixture infiltrated with the resin maybe coated. In some such arrangements, the coating may form an outerlayer of the composite body. In some arrangements, the coating may beany one or any combination of a spray metallization, fiber strands, afiber weave, metal plating, or dry powders. Coatings may be wholly orpartially made of zinc, aluminum, copper, steel, nickel, titanium,silver, gold, tantalum, cobalt chromium, or alloys of these metals aswell as cermets including tungsten carbide cobalt and ceramics includingalumina and chromium carbide.

In some arrangements, such fiber strands and such fiber weave may be anyone or any combination of fiberglass, carbon fiber, and an aramid fiber.In some arrangements, such fiber strands and such fiber weave may beembedded in the resin. In some arrangements, fiber strands may be anyone or any combination of chopped, loose, and mat. Such spraymetallization may be any one or any combination of an arc spraying,thermal or flame spraying, and kinetic or cold spraying.

In some arrangements, the coating may be metallic plating, such as butnot limited to any one or any combination of copper, nickel, and chromeplating. Metallic plating may be performed using electroplating orelectroless plating. In some examples of electroplating, electricallyconductive dry powders may be added to the resin before the resin fullycures or a conductive coating may be applied onto the composite body. Anelectrically charged plating material, e.g., electrolytic copper, maythen be applied to the conductive powders or other conductive coatingthat has been applied to the composite body.

In some arrangements, the dry powders may be metallic or ceramicparticles.

In some arrangements, the binder may be one part of a two-part curableresin.

In some arrangements, the coating may surround the bound mixtureinfiltrated with the resin. In some such arrangements, unbound particlesinside the coating may be removed.

In some arrangements, either or both of the first plurality of particlesand the second plurality of particles may be made of any one or anycombination of a sand, sodium bicarbonate, polymer, plaster, metal,ceramic, ash, organic powders, e.g., corn cob powder, including ediblepowders, and other particles which preferably may have a large surfacearea or may be porous and preferably may be more flexible, e.g.,relative to sand, including but not limited to engineered particles. Insome arrangements, either or both of the first plurality of particlesand the second plurality of particles may be solid. In somearrangements, either or both of the first plurality of particles and thesecond plurality of particles may be hollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are schematics illustrating steps for preparing a compositebody in accordance with an aspect of the technology;

FIG. 2 is a schematic of a composite assembly in accordance with anotheraspect of the technology;

FIG. 3 is a process flow diagram providing a summary of the steps forpreparing a composite body or assembly in accordance with another aspectof the technology;

FIGS. 4A and 4B are schematics illustrating steps for preparing acomposite body in accordance with another aspect of the technology;

FIG. 4C is a perspective view of the composite body of FIG. 4B;

FIGS. 4D-4F are schematics illustrating steps for preparing a compositeassembly from the composite body of FIG. 4B in accordance with anotheraspect of the technology;

FIGS. 5A and 5B are schematics illustrating steps for preparing acomposite body in accordance with another aspect of the technology;

FIG. 5C is a perspective view of the composite body of FIG. 5B;

FIGS. 5D-5F are schematics illustrating steps for preparing a compositeassembly from the composite body of FIG. 5B in accordance with anotheraspect of the technology;

FIG. 6 is a process flow diagram providing a summary of the steps forpreparing a composite body or assembly in accordance with another aspectof the technology;

FIGS. 7A and 7B are schematics illustrating steps for preparing anassembly of composite bodies in accordance with another aspect of thetechnology;

FIGS. 8A and 8B are schematics illustrating steps for preparing anassembly of composite bodies in accordance with another aspect of thetechnology;

FIG. 9 is a schematic of a composite body in accordance with anotheraspect of the technology; and

FIGS. 10A-10F are examples of articles prepared in accordance withvarious aspects of the technology.

DETAILED DESCRIPTION

Referring now to the example of FIGS. 1A-1C, composite body 100 is madeof base body 110 and cured resin 120. Base body 110 is formed of aplurality of particles bound by a liquid binder. The plurality ofparticles may be but are not limited to being silica sand or powderedmaterials, which may be but are not limited to being made from polymers,plaster, metals, ceramics, ash, salt, sodium bicarbonate, food materials(e.g., sugar, flour), and other powders dissolvable by water. Ceramics,as used herein, may be wholly or partially crystalline materialsincluding glass-ceramic, or noncrystalline materials including glass. Asin this example, the liquid binder of base body 110 may be 3D printedonto the plurality of particles using a binder jetting process. Variousbinders are used during such 3D printing processes, such as but notlimited to furan resin used by Voxeljet AG and the ExOne Company, LLC,“Part A” of a two-part curable resin system, e.g., a first part of atwo-part epoxy, phenolic, silicate, aqueous, and glycol. In somearrangements, an activator such as but not limited to certain acids,such as toluenesulfonic acid, is mixed with the plurality of particlesin order to activate certain binders that may be used, e.g., furanresin.

The plurality of particles of composite body 100 are loosely heldtogether by the binder such that the composite body is inherentlyporous. As demonstrated by FIG. 1B, resin 120, which may be but is notlimited to being a “Part B” of a two-part curable resin system, e.g., asecond part of a two-part epoxy, silicone, acrylic resin, and fiberreinforced plastic, is infiltrated or impregnated into an interior ofporous base body 110 through first surface 112 of base body 110 to aninterior edge 116 of resin 120. As in this example, resin 120 may form asurface of composite body 100. As demonstrated by FIG. 1C, in-processportions of base body 110 not infiltrated with resin 120 are removed. Inthis manner, the thickness of composite body 100 may be defined by thedepth of diffusion of resin 120 into base body 110 at edge 116 duringprocessing of the composite body, and thus the composite body may bestrengthened by resin 120 throughout an entire volume of the compositebody. In some arrangements, resin may be applied to base body 110 suchthat the resin fully infiltrates the entirety of the base body. In thismanner, no removal of portions of base body 110 without resin isnecessary. Such a configuration may be useful for preparing solidprototypes or tooling, or other functional parts.

As shown in FIG. 2, composite assembly 250 includes composite body 100and coating 260. As in this example, coating 260 may cover compositebody 100 at first surface 112 and at edge 116 of the composite body. Asin this example, coating 260 may extend partially into the compositebody 100, i.e., beneath surface 112 of base body 110 and edge 116 ofresin 120 (defining a surface of composite body 100), although in otherarrangements the coating may not extend into the composite body. Coating260 may be but is not limited to being a spray metallization, a carbonfiber layer, or a fiberglass layer.

Referring now to FIG. 3, composite body 100 and composite assembly 250may be prepared using process 300. As shown in step 370, a desiredprinted part, such as but not limited to base body 110, is designedusing computer-aided design and modeling (CAD) software, such as but notlimited to any CAD package configured to create 3D solid modelsconvertible to a format readable by the desired 3D printing machine.Such packages include but are not limited to SpaceClaim® 3D ModelingSoftware, SolidWorks® by Dassault Systemes, NX by Siemens ProductLifecycle Management Software Inc., Inventor®, 123D, and AutoCAD® byAutodesk®, and Geomagic® by 3D Systems, Inc. The drawing file generatedby the CAD software is then converted into the readable format, e.g., an.STL, .STP, 0.3MF, or .IGS file, for use by a 3D printing machine. Inalternative arrangements, the CAD package used may perform slicing ofthe 3D solid model and directly convert the model to machine codereadable by the 3D printing machine. At step 372, an in-process partcorresponding to the shape of the designed part is fabricated using a 3Dprinting machine, such as but not limited to any of model nos. VX-200,VX-500, VXC-800, VX-1000, VX-2000, and VX-4000 by Voxeljet AG, modelnos. Exerial, S-Max, M-Flex, Innovent, X1-Lab by The ExOne Company, LLC,model nos. 210, 310, 410, 450, and 650 by Zcorp, Inc., and model nos.ProJet CJP 260C, ProJet CJP 360, ProJet CJP 460Plus, ProJet CJP 660Pro,and ProJet CJP 860Pro by 3D Systems, Inc. In processing the in-processpart, a layer of a plurality of particles as described previously hereinis deposited on a table of the 3D printing machine or other suitablesubstrate placed on such table. A roller, brush, or scraper is typicallyused to evenly spread the plurality of particles. A liquid binder isthen extruded from a nozzle of the 3D printing machine to form a firstpatterned layer of loosely bound particles in the deposited layer of theplurality of particles, the patterned layer being a single layer of theprocessed part. After the first patterned layer is formed, the table andthus the particle bed is lowered, and a new layer of a plurality of theparticles is deposited over the previous patterned layer. Another layerof binder is then applied to the additional layer of the particles toform an additional patterned layer and to fuse the additional patternedlayer to the previous patterned layer. These depositing and patterningsub-steps are performed until a porous printed part, such as base body110, is formed.

At step 374, resin, such as but not limited to resin 120, is appliedeither or both of onto or beneath a surface of the printed part, such asfirst surface 112 of base body 110, and then infiltrates, i.e., absorbsand diffuses, into and through the printed part. Resin 120 preferablyshould be chosen so as not to soften the binder used to fabricate theprinted part and thereby weaken the printed part. The resin may beformed by but is not limited to being formed by any one or anycombination of polyester systems, acrylic systems, epoxy systems,polyurethane systems, cationic ultraviolet (UV) curable epoxy systems,epoxy-amine and cycloaliphatic epoxy systems, free radical UV curableacrylate systems, urethane systems including isocyanate-polyol andisocyanate-amine, cyanoacrylate. The resin may be applied onto theprinted part in a number ways. In some arrangements, the resin may beany one or any combination of brushed, rolled, or sprayed onto theprinted part, while in other arrangements, the printed part may besubmerged into the resin to infiltrate the printed part. When brushed,rolled, or sprayed onto the printed part, the depth of infiltration ofthe resin may be governed by the pot life and viscosity of the resin.When the printed part is submerged in the resin, infiltration of theresin throughout the entire volume of the printed part is made possible.To further enhance the depth of infiltration, a vacuum may be used toremove air in the printed part while the resin is along the surface orwithin the part, thereby creating a differential pressure duringintroduction of the resin. It is to be understood that as the amount ofresin introduced per area of any surface of the printed part increases,the deeper the resin flows into the printed part below the given surfacearea.

At step 375, the resin is cured, such as by the application of heat, orallowed to cure, such as by ambient air or forced air drying, in whichthe resin hardens. In this manner, the tensile and compressive strengthof the composite body is increased beyond the tensile and compressivestrengths of the printed part without the resin. At optional step 376, adry powder, i.e., additional particles, are added to at least a portionof the surface of the printed part infiltrated with the resin during thecuring stage of the resin. The dry powders may be any one or anycombination of brushed onto the printed part, sprayed onto the printedpart, or applied to the printed part by dipping the printed part into avolume of the dry powder. In some arrangements, the applied dry powderthen may be brushed to infuse the dry powder between the bound particlesof the printed part. In this manner, the surface of the part may besmoothened in which smoothening of the surface of the printed in-processpart, e.g., sanding on sand, is avoided. The resin infiltrated into theprinted part will wick into the dry powder and fill in gaps between theparticles of the dry powder. Different finishes may be formed by addingthe powder at different points throughout the curing cycle. The drypowder may be but is not limited to being any one or any combination ofaluminum, copper, steel, nickel, bronze, Teflon® coating, a ceramic, andalumina trihydrate.

At step 377, excess particles that are not bound by the cured resin arethen removed by way of any one or any combination of gravity, shaking,scraping, media blasting, other mechanical means, dissolution by waterwhen water soluble particles are used, and application of a vacuumcausing separation of loose particles from the portion of the printedpart bound by the cured resin to form a composite body, such ascomposite body 100.

At optional step 378, an exterior material, such as but not limited tocoating 260, is applied to one or more surfaces of the composite body,such as but not limited to composite body 100, to form a compositeassembly, such as composite assembly 250. In some arrangements, thecoating may be complete or chopped fiber strands or woven fibers. Suchfibers may be loose or may be formed into a mat. The fibers may be butare not limited to being made of fiberglass, carbon fiber, or an aramidfiber, e.g., Kevlar® fiber. The coating optionally may be applied duringthe curing of the resin such that such fibers may become embedded in theresin to form a composite with the resin upon curing of the resin.

In some arrangements, the coating may be metallic. In such arrangements,the coating may be applied using spray metallization. In somearrangements, the spray metallization used for coating may be any one orany combination of an arc spraying, thermal or flame spraying such asthat used by Flame Spray Inc., and kinetic or cold spraying. Inpreferable arrangements, the coating may be wholly or partially made ofzinc, aluminum, copper, steel, nickel, titanium, silver, gold, tantalum,cobalt chromium, or alloys of these metals as well as cermets includingtungsten carbide cobalt and ceramics including alumina and chromiumcarbide.

In some arrangements, the coating may be metallic plating, such as butnot limited to any one or any combination of copper, nickel, and chromeplating. Metallic plating may be performed using electroplating orelectroless plating. In some examples of electroplating, electricallyconductive dry powders, i.e., particles, may be added to the resinbefore the resin fully cures as at step 376 or a conductive coating maybe applied, such as by spraying, onto the composite body. Anelectrically charged plating material, e.g., electrolytic copper, maythen be applied to the conductive powders or other conductive coatingthat has been applied to the composite body.

In some arrangements, the exterior material may be a topcoat, such asbut not limited to a paint or resin which may have different propertiesthan the resin infiltrating the printed part. In this manner, thecomposite body may be given a variety of surface finishes. The topcoatmay be color tinted to provide a desirable finish color. The topcoat maybe a metal-filled resin to provide additional strength and wearproperties as well as to create a desired metallic effect. The same ordifferent topcoats may be layered to provide different surface effects.

Referring again to FIG. 1B, in an alternative arrangement of compositebody 100, resin 120 is infiltrated through second surface 114 of basebody 110 opposite first surface 112 of the base body in addition tobeing infiltrated through first surface 112. In this arrangement, theresin that infiltrates both first surface 112 and second surface 114 iscured after infiltration. Such additional infiltration allows for thefabrication of either or both of thicker and larger volume compositebodies.

In some alternative arrangements, the base body may be formed asdescribed previously herein such that the porosity of either of firstsurface 112 of base body 110 and second surface 114 of the base body maybe greater than the porosity of the other of the first and secondsurfaces of the base body. In this manner, when resin 120 is infiltratedinto the base body, the strength on the side of the formed compositebody adjacent to the first surface of the base body may be differentthan the strength on the side of the formed composite body adjacent tothe second surface of the base body.

In some arrangements, the porosity of the printed part may becontrolled. In such arrangements, the patterned layers may be formed ina random, e.g., non-repeating, order or in a repeating pattern, e.g., asa plurality of tessellated unit cells. Such unit cells may be in theform of polyhedra, such as but not limited to tetrahedra, octahedra, anddodecahedra.

Referring to FIGS. 4A-4C, base body 410 used in the formation ofcomposite body 400 is the same or substantially the same as base body110 with the exception that base body 410 includes first base bodysection 410A and second base body section 410B extending from the firstbase body section. Both first and second base body sections 410A, 410Bmay be inherently porous in the same manner as base body 110. In theexample shown, second base body section 410B is made up of tessellatedunit cells that define a plurality of cubes. Each cube shares at leastone face with another cube of second base body section 410B. Such apattern provides rigidity for handling of base body 410 and subsequentlycomposite body 400 while being easier to remove, due to its lowerdensity, than the portion of base body 110 removed from the rest of basebody 110 in the formation of composite body 100. This pattern or othersuch patterns defining large pores may be formed using an additivemanufacturing machine in a manner similar to that described previouslyherein with respect to composite body 100 and composite assembly 250that, for example, may apply a binder to particles at only predeterminedlocations of each layer during a build process forming a printed part.In this manner, gaps 404 filled with unbound particles may be formedbetween the plurality of cubes of second base body 410B.

As demonstrated by FIG. 4B, resin is infiltrated into an interior offirst base body section 410A up to at least the intersection of firstbody section 410A and second base body section 410B, i.e., latticevolume V_(L), in the same or a substantially similar manner that resin120 is applied to base body 110 in forming composite body 100. As shownin FIG. 4D, in the same manner as the example shown in FIG. 2, coating260 may be applied to first base body section 410A. As shown in FIG. 4E,second base body section 410B may be severed from first base bodysection 410A at cut plane 440 to form composite body 400. As shown inFIG. 4F, coating 260 is applied to the side of first base body section410A severed from second base body section 410B. In this manner,composite assembly 450 is formed in which the composite assembly is thesame or substantially the same as composite assembly 250.

Referring now to FIGS. 5A-5C, base body 510 used in the formation ofcomposite body 500 is the same or substantially the same as base body410 with the exception that base body 510 includes first base bodysection 510A and second base body section 510B extending from the firstbase body section. Both first and second base body sections 510A, 510Bmay be inherently porous in the same manner as base body 410 (andtransitively base body 110). Base body 510 is formed, such as by theadditive manufacturing process described previously herein, such thatfirst base body section 510A meets second base body section 510B at aperimeter of the base body. In this manner, gaps 504 filled with unboundparticles may be formed between the first and second base bodies 510A,MOB. In this manner, the first and second base bodies 510A, 510B may besevered from each other more easily than removing a portion of base body110 in the example of forming composite body 100.

As demonstrated by FIG. 5B, resin is infiltrated into an interior offirst base body section 510A up to at least the intersection of firstbody section 510A and second base body section 510B in the same or asubstantially similar manner that resin 120 is applied to base body 110in forming composite body 100 and resin 420 is applied to base body 410in forming composite body 400. As shown in FIG. 5D, in the same manneras the example shown in FIGS. 2 and 4D, coating 260 may be applied tofirst base body section 510A. As shown in FIG. 5E, second base bodysection 510B may be severed from first base body section 510A to formcomposite body 500. As shown in FIG. 5F, coating 260 is applied to theside of first base body section 510A severed from second base bodysection 510B. In this manner, composite assembly 550 is formed in whichthe composite assembly is the same or substantially the same ascomposite assemblies 250, 450.

As shown in FIG. 6, composite bodies 400, 500 and composite assemblies450, 500 may be prepared using process 600. At step 670, a desiredprinted part, such as but not limited to base bodies 410, 510 aredesigned in the same manner as described previously herein with respectto step 370 of process 300. At step 672, an in-process partcorresponding to the shape of the designed part is fabricated using a 3Dprinting machine in the same manner as described previously herein withrespect to step 372 of process 300. At step 674, resin, such as but notlimited to resin 420, 520 is applied either or both of onto or beneath asurface of the printed part in the same manner resin 120 is applied tothe printed part as described previously herein with respect to step 374of process 300. At step 675, the resin is cured or allowed to cure inthe same manner the resin is cured or allowed to cure as describedpreviously herein with respect to step 375 of process 300. At optionalstep 676, fibers may be applied to the resin infiltrated surface of theprinted in-process part to form a composite lay-up. Such fibers may bein the form of any of the complete or chopped fiber strands or wovenfibers as described previously herein with respect to step 378 ofprocess 300. At step 677, sections of the in-process part, such assecond base body sections 410B, 510B are severed from the in-processpart, such as first base body sections 410A, 410B infiltrated withresin, and any particles not bound by the resin are removed. At optionalstep 678, an exterior material, such as but not limited to coating 260,is applied to one or more surfaces of the composite body, such as butnot limited to composite bodies 400, 500 to form a composite assembly,such as composite assemblies 450, 550. Such exterior material may be inthe form of the exterior material described previously herein withrespect to step 378 of process 300. In some arrangements, any of thesteps of process 600 may be used with process 300 and vice versa. Asexamples, steps 676 and 677 may be utilized with process 300 and step375 may be utilized with process 600.

In some arrangements for preparing composite assemblies for use assacrificial tooling, which preferably may include the use of process 300or process 600, an in-process composite body may be coated but is notlimited to being coated by plating copper, by hydroforming sheet metal,by spray metallizing, or by plating copper followed by hydroforming orspray metallizing onto one or more surfaces, and in many arrangementsthe entirety of the exterior, of the in-process composite body to adesired thickness for the coating (and thus the coated composite body atthis stage). Subsequently, the coating is separated from the in-processcomposite body by dissolving the in-process composite body with anappropriate solvent, e.g., methylene chloride. In some arrangements, inaddition to dissolving the in-process composite body, the copper platingwhen used may also be dissolved, for example, by applying sulfuric acidto the coating.

Referring now to FIGS. 7A and 7B, resin 720 may be infiltrated into eachof base bodies 710A, 710B, which preferably may be 3D printed partsprepared using process 300 or alternatively process 600 in which in somearrangements tessellated unit cells may be formed (see FIGS. 4A-4C),through respective concave inner surfaces 712A, 712B and cured. Basebodies 710A, 710B may have a thickness sufficient to absorb resin 720 toa predetermined depth of diffusion at respective edges 716A, 716B ofresin 720, as in the example of FIG. 7A. As shown by the differencesbetween FIGS. 7A and 7B, sections between respective edges 716A, 716B ofresin 720 and convex outer surfaces 714A, 714B which are not infiltratedwith resin are removed to leave respective composite bodies 700A, 700B.As in this example, base bodies 710A, 710B and composite bodies 700A,700B may be symmetrical to each other such that end surfaces 715A, 715Bof respective composite bodies 700A, 700B may be adhered together, suchas by but not limited to being by an epoxy, to form hollow article 790.In some arrangements, hollow article 790 may include part line 791 atthe interface of composite bodies 700A, 700B. As in the example of FIG.2, a coating, which may be but is not limited to being a spraymetallization or fiberglass, may be applied to cured inner surfaces712A, 712B to further strengthen either or both composite bodies 700A,700B.

As shown in FIGS. 8A and 8B, in a similar arrangement to that shown inFIGS. 7A and 7B, resin may be infiltrated into each of base bodies 810A,810B, which preferably may be 3D printed parts prepared using process300 or alternatively process 600 in which in some arrangementstessellated unit cells may be formed (see FIGS. 4A-4C), through convexouter surfaces and cured. The portions of base bodies 810A, 810B whichare not infiltrated with resin are removed to leave respective compositebodies 800A, 800B. In a similar manner to the formation of hollowarticle 790, in this example, composite bodies 800A, 800B may besymmetrical to each other such that their end surfaces may be adheredtogether, such as by but not limited to being by an epoxy, to formhollow article 890.

Referring now to FIG. 9, composite body 900 includes base body 910infiltrated by resin 920. Base body 910 is formed of a plurality ofparticles bound by a liquid binder. As shown, base body 910 isinfiltrated by resin 920 to edge 920A such that the resin-infiltratedbase body surrounds and retains the remainder of the base body that isnot infiltrated by the resin. In this manner, for some applications,removal of the portion of the base body that is not infiltrated by theresin is unnecessary. In some alternative arrangements, the portion ofthe base body that is not infiltrated by the resin may be formed ofeither or both different particles and a different binder than those ofthe base body used to form the resin-infiltrated base body. In somealternative arrangements, the portion of the base body that is notinfiltrated by the resin and is surrounded by the resin-infiltrated basebody may be a combination of unbound particles, i.e., particles that arenot bound by a binder, and bound particles, i.e., particles bound by abinder, or may be only unbound particles.

The technology described herein may be used in a number of applications.Some possible end uses include prototype parts for display, exhibit,testing, etc.; large waterproof prototypes such as for kitchen andbathroom fixtures including but not limited to countertops, sinks,toilets, and showers as well as for commercial/industrial tanks, etc.;forming tools for hydroforming, stamping, vacuum forming; casting toolsfor resins, polymers, low melt alloys, and cementitious products; lay-uptools for composite products; metal plated parts; decorative platedparts; hammer bucks and fitment bucks, especially for automotiveapplications; jigs and fixtures; art, sculpture, portraiture, and customparts; monuments and memorials; and signage. To fabricate a thin shellstructure, such as a panel, curable resin may be applied to a base bodyas described previously herein and excess particles of the base body maybe removed to form a composite body in which the resin is infiltratedthroughout the thickness of the composite body. The base body may be 3Dprinted as described previously herein. If additional strength orrigidity is needed, then the composite body in the form of the panel maybe used as a core and one or more layers of additional materials, suchas but not limited to fiberglass or carbon fiber, may be added to thecomposite body panel. For a car body or other panels requiring evengreater strength, composite materials may be layered within the basebody.

For a large sculpture requiring additional strength, a composite body asdescribed previously herein may be backfilled with a rigid foam,cementitious products, or other rigid backfilling materials. Forstamping tooling or other tooling, curable resin may be added to theimpact side or portion of a base body of sufficient thickness forhandling while either applying or not applying resin through a side ofthe base body opposite the impact side or portion, depending on thestrength needed. For two-part stamping tooling, single sidedhydroforming tooling, and fiber composite layup tooling, a curable resinmay be applied to a base body as described previously herein as abackfill.

In some arrangements, surface treatments may be applied to any suchcomposite bodies, such as for car body or other panels or for toolingrequiring such treatments. Once a 3D printed part or other base body isinfiltrated, the base body may be coated with a curable resin on anouter surface to be exposed to smooth the surface. Such coating may havefillers such as but not limited to ceramic powder, metal powder, metalfillings including but not limited to metal shavings and filings,plastic powder, and organic powders such as wood flour added to givedesired properties. Inner surfaces opposite such outer faces may also oralternatively be coated with a curable resin as well. As describedpreviously herein, these resin-coated surfaces further may be spraymetallized with an appropriate metal.

In molding applications, a curable resin or composite may be applied toa 3D printed or other base body of bound particles to form permanent orother reusable molds (e.g., casting mold, roto-mold, etc.) in contrastto a destructible mold in which no strengthening material is generallyneeded, vacuum-forming, or thermoforming molds.

It is to be further understood that the disclosure set forth hereinincludes any possible combinations of the particular features set forthabove, whether specifically disclosed herein or not. For example, wherea particular feature is disclosed in the context of a particular aspect,arrangement, configuration, or embodiment, that feature can also beused, to the extent possible, in combination with and/or in the contextof other particular aspects, arrangements, configurations, andembodiments of the technology, and in the technology generally.

Furthermore, although the technology herein has been described withreference to particular features, it is to be understood that thesefeatures are merely illustrative of the principles and applications ofthe present technology. It is therefore to be understood that numerousmodifications, including changes in the sizes of the various featuresdescribed herein, may be made to the illustrative embodiments and thatother arrangements may be devised without departing from the spirit andscope of the present technology. In this regard, the present technologyencompasses numerous additional features in addition to those specificfeatures set forth in the claims below. Moreover, the foregoingdisclosure should be taken by way of illustration rather than by way oflimitation as the present technology is defined by the claims set forthbelow.

The invention claimed is:
 1. A 3D printed composite body, comprising: abound mixture including a binder and a plurality of particles includingbound and unbound particles, the bound mixture being porous; a resininfiltrating the bound mixture to strengthen the bound mixture; and acoating applied to an exterior surface of the bound mixture strengthenedby the resin, wherein the coating infiltrates at least a portion of thebound mixture.
 2. The composite body of claim 1, wherein the coatingincludes a filler being one of ceramic powder and polymer powder.
 3. Thecomposite body of claim 1, wherein the coating has a first thicknessless than a second thickness defined by the bound mixture.
 4. Thecomposite body of claim 1, wherein the coating is applied to theexterior surface of the bound mixture by any one or any combination of aspray metallization, fiber strands, a fiber weave, metal plating, anddry powders.
 5. The composite body of claim 1, wherein the binder is onepart of a two-part curable resin.
 6. The composite body of claim 1,wherein the plurality of particles are made of any one or anycombination of a sand, sodium bicarbonate, polymer, plaster, metal,ceramic, ash, and organic powders.
 7. The composite body of claim 1,wherein the resin is applied to the bound mixture from a plurality ofdirections to define a part line.
 8. The composite body of claim 1,wherein the porous bound mixture defines a gradient porosity.
 9. Thecomposite body of claim 1, wherein an interior surface of the boundmixture is less porous than the exterior surface of the bound mixture.10. The composite body of claim 1, wherein the bound mixture definespores into which the resin is infiltrated, the resin filling a pluralityof pores of the bound mixture.
 11. The composite body of claim 1,wherein at least a portion of the unbound particles is not infiltratedby the resin.
 12. The composite body of claim 1, wherein at least aportion of the bound mixture is not infiltrated by the resin.
 13. Thecomposite body of claim 1, wherein at least a portion of the boundmixture is not infiltrated by the coating.
 14. A method of forming a 3Dprinted composite body, comprising the steps of: combining a pluralityof particles including bound and unbound particles with a binder to forma porous bound mixture; infiltrating the bound mixture with a resin tostrengthen the bound mixture; and applying a coating to the exteriorsurface of the bound mixture, the coating having a first thickness lessthan a second thickness defined by the bound mixture, and wherein thecoating infiltrates at least a portion of the bound mixture.
 15. Themethod of claim 14, further comprising the step of: removing at least aportion of the bound mixture.
 16. The method of claim 14, wherein thecombining step includes forming the bound mixture around the unboundparticles.
 17. The method of claim 16, further comprising the step of:removing the unbound particles and the bound mixture.
 18. The method ofclaim 14, wherein the coating is a metal plating.
 19. The method ofclaim 18, further comprising the step of: removing at least a portion ofthe bound mixture from the coating.